A patterning technology producing a micro- or nano-sized 3-dimensional structure in a desired position by selectively controlling charged particles plays an important role in developing materials having new physical and chemical characteristics.
Particularly, producing a 3-dimensional nanostructure by improving focusing effect is expected to be useful in terms of producing future optical, electrical or magnetic devices.
For patterning charged particles, in the beginning, patterning, i.e., position controlling and attaching, of the particles was conducted by forming a dielectric film on a conductive or nonconductive support, and transferring an electric charge on the dielectric film by using a process such as electron beam or ion beam focusing (SEM or FIB), an atomic force microscope (AFM), micro-contact printing and the like.
According to study results released since 2003, a method for electrofocusing deposition of charged particles in a desired pattern position including the steps of forming a photo-resistor on a support; patterning the formed photo-resistor; and implanting charged particles while controlling charges on the photo-resistor surface by using electrical field formation and ion charge implantation, has been introduced.
However, in the case of forming a photo-resistor on a support as described above, there are inconveniences that the photo-resistor cannot be reused and photo-resistor patterning should be conducted several times to form a 3-dimensional structure system. Further, it is not suitable as a future technology of nano-sized or atomic level patterning because it is difficult to control the surface ion charges.
On the other hand, in the case of vacuum deposition, a metal mask having a pattern of perforations can be used, and in this case, there are problems that it is difficult to produce a nano-sized pattern and material loss resulting from mask contamination is very big when the aspect ratio is high. Further, in the case of electron beam photolithography (EPL), although a nano-sized pattern can be produced, the pattern size may be irregularly reduced due to the material attached (contaminated) to the mask surface.
Accordingly, in Korean Patent Registration No. 10-0907787, the present inventors suggested a method for focused patterning of charged particles comprising the steps of placing a mask having a pattern of perforations on a substrate and guiding charged particles to the substrate through the perforations, followed by focused deposition of the particles on the substrate (see FIG. 1). As shown in FIG. 1, equipotential lines (9) and electric field lines (10) are formed by applying voltage between two electrode layers (5), (6) in a grounded reactor (metal chamber) (30). Charged particles (1) move along the electric field lines (10) by electrical force and then migrate to a substrate (3). A pattern structure (4) on the substrate (3) is formed by focusing the charged particles (1) passing through a nonconductive plate or film (2) by an electrodynamic lens. However, only 2-dimensional patterns can be formed by this method.
Thus, the present inventors have further studied a more efficient method for producing a nanoparticle assembly structure having 3-dimensional shape.